Quick overview of what you’ll learn from this blog post:
- How caloric restriction serves as the basis for popular diet systems
- What exactly is meant by caloric restriction
- How caloric restriction can transcend weight loss and support wellness
- The supporting research
- CALERIE and what’s next in the field
The notion of fasted dieting has become a trend among elite athletes and celebrities – those whose livelihoods are primarily contingent on physical appearance and performance. But is this approach to nutrition the magic bullet for weight management and general health, or is it the latest in a long line of fad diets?
We all remember the era of fat-free – a widely held misconception that dietary fat was the source of weight management issues. Years later, we’d come to understand how many of these products were able to maintain the sensibilities of full-fat foods – mainly with sugar and other unhealthy preservatives.
Conversely, the Atkins diet is built almost entirely on dietary fat as dieters altogether remove carbohydrates from their diets. Ironically, and to much public outrage, a state medical examiner’s report revealed that Dr. Robert Atkins, the namesake of the low-carb craze, had a history of heart attack, congestive heart failure, and hypertension.
Still, millions of Atkins disciples lost weight and achieved health goals. The same is true for followers of South Beach, the Weight Watchers’ point system, Keto, the Vertical Diet, TB12, a vegan diet, etc.
This lends the question: what is common to each of these popular programs that facilitates effective weight loss and allows dieters to at least temporarily find a path back towards wellness?
Ultimately, the element which underlies the success or effectiveness of any diet is caloric restriction. And so, the popular diet systems mentioned above all function as a way to make CR a little more tolerable for dieters so they can stick to the new nutritional habits over time. The need to bolster the sustainability of restrictive eating habits is rooted in the simple fact that eating in a caloric deficit can be grueling and even physically uncomfortable.
But if weight loss is so difficult, why bother with CR at all? Intuitively, we understand the health risks associated with overeating and obesity, and certainly, we all want to look a bit better on the beach. But aside from weight loss and improved body composition, there is evidence that a calorie-restrictive diet may also contribute to longevity in ways not often considered.
Calorie Restriction Explained
First, it is vital to appropriately define caloric restriction as it relates to longevity. In this context, the goal is not necessarily to lose weight. Instead, a reduction of average daily calories – typically due to fasting – can lead to increased lifespans and lowered risk of age related diseases, including certain cancers. This is in addition to the health issues we typically associate with obesity like diabetes and heart disease.
It is important to note that up unto this point, there is no data in humans on the relationship between calorie restriction and longevity. What information we do have is the product of decades of research involving various animals including worms, crabs, snails, rodents, monkeys, and others. That said, it is possible the physiological response to caloric restriction in humans is completely unique.
What Can We Learn From CALERIE?
Recently, however, the National Institute of Aging supported a Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE). The study looked at two groups of middle-aged, normal to moderately overweight adults, one which followed a calorie restrictive diet, and a control group. After two years, the CR group predictably lost weight, and reduced blood pressure and cholesterol. More importantly, though, these individuals showed decreases in some inflammatory factors and thyroid hormones – two markers connected to age related disease when trending high. The CR group also experienced some favorable effects on mood, sexual function, and sleep.
Compared to a decreased risk of heart disease and stroke, the effect of CR on inflammatory factors and thyroid hormones may seem inconsequential. Really, though, these results are a bit of a breakthrough. Up to this point, studies of calorie restriction have not controlled for the ancillary effect of weight loss. There is no question that reducing intake will improve markers like cholesterol, atherosclerosis, blood glucose levels, insulin resistance, and blood pressure, predictive of heart disease, stroke, and diabetes, especially for moderately overweight individuals. This has left the anti-aging community wondering whether there are any alternative longevity benefits mutually exclusive weight loss.
What’s Next for CR Research?
The CALERIE trial provided the first evidence tied to humans that “caloric restriction affects many processes that have been proposed to regulate the rate of aging.” Previously, CR trials on lab animals had demonstrated improved rates of inflammation, oxidative stress, and sugar metabolism; the ability to maintain protein structures, provide energy for cellular processes; and modify DNA. Calorie restriction in the human CALERIE trial affected several of these processes similarly.
Still, more purposeful clinical research is needed to concretize findings and legitimize anti-aging claims associated with various CR diets. For example, the NIA is currently testing the 5:2 diet in obese individuals aged 55 to 70 with insulin resistance. 5:2 refers to days of daily eating wherein, every five days, dieters limit themselves to 500-600 calories for the next two days. The experiment will determine how the 5:2 diet affects insulin resistance compared to a normal diet and the brain chemistry at play in Alzheimer’s disease.
We’ll keep our finger on the pulse of this important work and continue to provide updates as information is made available!